Method of expecting n20 generation according to oxidation of nh3 in sdpf

ABSTRACT

A method of expecting N 2 O generation according to oxidation of NH 3  in an SDPF according to an exemplary embodiment of the present invention may include measuring an initial NH 3  absorption amount in the SDPF, determining a first middle NH=3 absorption amount by subtracting an NH 3  slip amount in the SDPF from the initial NH 3  absorption amount in the SDPF, determining a second middle NH 3  absorption amount by subtracting an NH 3  amount oxidizing to NO x  and N 2  from the first middle NH 3  absorption amount, determining N 2 O generation amount in the SDPF, and determining a final NH 3  absorption amount in the SDPF by subtracting the N 2 O generation amount from the second middle NH 3  absorption amount.

CROSS-REFERENCE(S) TO RELATED APPLICATIONS

The present application claims priority to Korean Patent Application No. 10-2017-0092922, filed on Jul. 21, 2017, the entire contents of which are incorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a method of expecting N₂O generation, and, more particularly, the present invention relates to a method of expecting N₂O generation according to oxidation of NH₃ in an SDPF by using NO₂ generation factor.

Description of Related Art

Generally, exhaust gas which is expelled through an exhaust manifold of an engine is induced to pass through a catalytic converter which is mounted in a middle portion of an exhaust pipe to be purified, and noise thereof is reduced while passing through a muffler before the exhaust gas is discharged to externally through a tail pipe.

The catalytic converter processes the pollution materials that are included in the exhaust gas. Furthermore, a particulate filter is mounted on the exhaust pipe to trap particulate material (PM) which is included in the exhaust gas.

A selective reduction catalytic device is a type of catalytic converter. Reducing agents including carbon monoxide, total hydrocarbon (THC), and the like react well with nitrogen oxide rather than oxygen in the selective catalyst reduction apparatus (SCR), hence the name “a selective catalyst reduction apparatus (SCR)”.

The particulate filter (Diesel Particulate Filter) is disposed at an exhaust pipe and collects particulate matter included in the exhaust gas, and reduces the nitrogen oxide included in the exhaust gas using reducing agent injected from an injection module. For the provided purpose, the particulate filter may include selective catalytic reduction on diesel particulate filer (SDPF) and additional selective catalytic reduction.

In a case of an internal combustion engine to which the selective catalyst reduction apparatus is disposed, in a normal driving mode of a diesel engine with an oxygen rich environment, a nitrogen oxide exhausted from the engine and ammonia generated by a urea directly injected and supplied to the exhaust pipe are selectively reacted wherein the nitrogen oxide is converted into harmless nitrogen (N₂) and then is removed.

When ammonia (NH₃) absorbed in the SDPF is exposed to a high temperature, N₂O is generated by an oxidation reaction of the NH₃.

The amount of generated N₂O is approximately 300 times the amount that CO₂ affects global warming, therefore effort to reduce generation of the N₂O exists.

The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the related art already known to a person of skilled in the art.

BRIEF SUMMARY

Various aspects of the present invention are directed to providing a control logic configured to predict N₂O generation amount according to NH₃ oxidation in a selective catalytic reduction on diesel particulate filter (SDPF) and improves prediction of NO_(x) and NH₃ slip at a rear end portion of the SDPF.

A method of expecting N₂O generation according to oxidation of NH₃ in the SDPF according to an exemplary embodiment of the present invention may include measuring initial NH₃ absorption amount in the SDPF, determining a first middle NH₃ absorption amount by subtracting NH₃ slip amount in the SDPF from the initial NH₃ absorption amount in the SDPF, determining a second middle NH₃ absorption amount by subtracting an NH₃ amount oxidizing to NO_(x) and N₂ from the first middle NH₃ absorption amount, determining N₂O generation amount in the SDPF, and determining a final NH₃ absorption amount in the SDPF by subtracting the N₂O generation amount from the second middle NH₃ absorption amount.

In determining the first middle NH₃ absorption amount, the NH₃ slip amount in the SDPF may be a value determined by multiplying the initial NH₃ absorption amount and an NH₃ slip factor.

In determining the second middle NH₃ absorption amount, the NH₃ amount oxidizing to NO_(x) and N₂ may be a value determined by multiplying the first middle NH₃ absorption amount and an oxidation factor oxidizing to NO_(x) and N₂.

In determining N₂O generation amount in the SDPF, the N₂O generation amount may be a value determined by multiplying the second middle NH₃ absorption amount and the N₂O generation factor.

The N₂O generation factor may be determined by considering SCR catalyst temperature, an NH₃ absorption ratio in the SDPF, an exhaust gas flow amount, NO density, and degree of catalyst degradation.

The SCR catalyst temperature may be determined by measuring the exhaust gas temperature.

The NO gas amount may be determined by measuring NO density.

The degree of catalyst degradation may be determined by a catalyst degradation map applying a catalyst degradation factor.

The N₂O generation factor may be determined by determining a first value by applying the SCR catalyst temperature and the NH₃ absorption ratio in the SDPF to the first map, determining a second value by applying the exhaust gas flow amount and the NO density to a second map, determining a third value by applying the catalyst degradation factor to a third map, and multiplying the first value, the second value, and the third value together.

A method of expecting N₂O generation according to oxidation of NH₃ in the SDPF according to an exemplary embodiment of the present invention may further include determining N₂O slip amount by applying a transform constant using a map to the N₂O generation amount, and determining NH₃ slip amount by subtracting the NO₂ generation amount from the initial NH₃ absorption amount in the SDPF.

According to an exemplary embodiment of the present invention, modeling accuracy of the oxidation by-products may be improved.

Also, expectation of slip of NO_(x) and NH₃ at the rear end portion of the SDPF may be improved.

Also, through improvement of SDPF modeling accuracy, catalyst capacity may be decreased and manufacturing cost may be reduced.

The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sequential chart illustrating a method of expecting N₂O generation according to oxidation of NH₃ in an SDPF according to an exemplary embodiment of the present invention;

FIG. 2 is a sequential chart illustrating a method of determining N₂O generation factor in the method of expecting N₂O generation according to oxidation of NH₃ in an SDPF according to an exemplary embodiment of the present invention;

FIG. 3 is a flowchart illustrating a method of expecting N₂O generation according to oxidation of NH₃ in an SDPF according to an exemplary embodiment of the present invention illustrated in FIG. 1;

FIG. 4 is a flowchart illustrating a method of determining N₂O generation factor illustrated in FIG. 2; and

FIG. 5 is a graph showing a difference between final NH₃ absorption amount in an SDPF according to a method of expecting N₂O generation according to oxidation of NH₃ in the SDPF according to an exemplary embodiment of the present invention and an actual measurement value.

It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the invention. The specific design features of the present invention as disclosed herein, including, for example, specific features of the present invention as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particular intended application and use environment.

In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that the present description is not intended to limit the invention(S) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

Furthermore, in exemplary embodiments, since like reference numerals designate like elements having the same configuration, a first exemplary embodiment is representatively described, and in other exemplary embodiments, only different configurations from the first exemplary embodiment will be described.

The drawings are schematic and are not illustrated in accordance with a scale. The relative sizes and ratios of the parts in the drawings are exaggerated or reduced for clarity and convenience, and the arbitrary sizes are only exemplary and are not limiting. The same structures, elements, or parts illustrated in no less than two drawings are denoted by the same reference numerals to represent similar characteristics. When a part is referred to as being “on” another portion, it can be directly on the other part or intervening parts may also be present.

Furthermore, the exemplary embodiments are not limited to a specific shape of an illustrated region, but, for example, include changes in shape in accordance with manufacturing.

Now, method of expecting N₂O generation according to oxidation of NH₃ in an SDPF according to an exemplary embodiment of the present invention will be described with reference to FIG. 1 and FIG. 3.

FIG. 1 is a sequential chart illustrating a method of expecting N₂O generation according to oxidation of NH₃ in the SDPF according to an exemplary embodiment of the present invention, and FIG. 3 is a flowchart illustrating a method of expecting N₂O generation according to oxidation of NH₃ in the SDPF according to an exemplary embodiment of the present invention illustrated in FIG. 1.

Referring to FIG. 1 and FIG. 3, first, initial NH₃ absorption amount (A, 100) in the SDPF is measured (S101).

As such, a first middle NH₃ absorption amount (B, 200) is determined by subtracting the NH₃ slip amount in the SDPF from the initial NH=3 absorption amount (A, 100) in the SDPF (S102). At the present time, the NH₃ slip amount in the SDPF may be a value determined by multiplying the initial NH₃ absorption amount (A, 100) and an NH₃ slip factor.

As such, a second middle NH₃ absorption amount (C, 300) is determined by subtracting the NH=3 amount oxidizing to NO_(x) and N₂ from the first middle NH₃ absorption amount (B, 200) (S103). At the present time, the NH₃ amount oxidizing to NO_(x) and N₂ may be a value determined by multiplying the first middle NH₃ absorption amount (B, 200) and an oxidation factor oxidizing to NO_(x) and N₂.

As such, N₂O generation amount in the SDPF is determined (S104), and a final NH₃ absorption amount (final, 400) in the SDPF by subtracting the N₂O generation amount from the second middle NH₃ absorption amount (C, 300) (S105). At the present time, the N₂O generation amount may be a value determined by multiplying the second middle NH=3 absorption amount (C, 300) and the N₂O generation factor.

Meanwhile, method of expecting N₂O generation according to oxidation of NH₃ in the SDPF according to an exemplary embodiment of the present invention may further include determining N₂O slip amount by applying a transform constant using a map to the N₂O generation amount (S106), and determining NH₃ slip amount by subtracting the NO₂ generation amount from the initial NH₃ absorption amount (A, 100) in the SDPF (S107).

For example, when the final NH₃ absorption amount (final) is 100 mmol by applying method of expecting N₂O generation according to oxidation of NH₃ in the SDPF according to an exemplary embodiment of the present invention, the final NH₃ absorption amount (final) may be 98 mmol when the method of expecting according to an exemplary embodiment of the present invention is not applied. The final NH₃ absorption amount (final) which is 98 mmol becomes current absorption amount, and when NH₃ amount absorbed in the SDPF when urea is injected is 2 mmol, the total absorption NH₃ amount becomes 100 mmol. However, when the method of expecting according to an exemplary embodiment of the present invention is not applied, the total absorption NH₃ amount becomes 102 mmol.

When the total absorption NH₃ amount is 102 mmol, oxidation amount and N₂O slip amount becomes more than when the total absorption NH₃ amount is 100 mmol. The absorption amount accumulates, therefore the error value becomes larger.

FIG. 2 is a sequential chart illustrating a method of determining N₂O generation factor in the method of expecting N₂O generation according to oxidation of NH₃ in the SDPF according to an exemplary embodiment of the present invention, and FIG. 4 is a flowchart illustrating a method of determining N₂O generation factor illustrated in FIG. 2.

Referring to FIG. 2 and FIG. 4, in the step of determining N₂O generation amount in the SDPF (S104), the N₂O generation factor may be determined by considering SCR catalyst temperature, an NH₃ absorption ratio in the SDPF, an exhaust gas flow amount, NO density, and a degree of catalyst degradation.

The SCR catalyst temperature may be determined by measuring the exhaust gas temperature, the NO gas amount may be determined by measuring NO density, and the degree of catalyst degradation may be determined by a catalyst degradation map applying a catalyst degradation factor.

Meanwhile, N₂O generation factor may be determined by determining a first value by applying the SCR catalyst temperature and the NH₃ absorption ratio in the SDPF to the first map 10 (S201), determining a second value by applying the exhaust gas flow amount and the NO density to a second map 20 (S202), determining a third value by applying the catalyst degradation factor to a third map 30 (S203), and multiplying the first value, the second value, and the third value together (S204). The first map 10 may be a map including numerical values predetermined by experiment of NH₃ absorption in the SDPF with respect to a temperature of the SCR catalyst, the second map 20 may be a map including numerical values predetermined by experiment of NO density with respect to the exhaust gas flow amount, and the third map 30 may be a map including numerical values predetermined by experiment of the degree of catalyst degradation with respect to time.

FIG. 5 is a graph showing a difference between final NH₃ absorption amount in the SDPF according to a method of expecting N₂O generation according to oxidation of NH₃ in the SDPF according to an exemplary embodiment of the present invention and an actual measurement value.

Referring to FIG. 5, in a transient driving mode, the final NH₃ absorption amount in the SDPF increases as time passes.

A difference between the NH₃ absorption amount (NH₃ accumulation amount) when the method of expecting according to an exemplary embodiment of the present invention is not applied and an actual measurement value is greater than a difference between the NH₃ absorption amount (NH₃ accumulation amount) when applied and an actual measurement value.

By applying method of expecting N₂O generation according to oxidation of NH₃ in the SDPF according to an exemplary embodiment of the present invention, the error value between the NH₃ absorption amount and the actual measurement value may be reduced.

Like the above, according to an exemplary embodiment of the present invention, modeling accuracy of the oxidation by-products may be improved.

Also, expectation of slip of NO_(x) and NH₃ at the rear end portion of the SDPF may be improved.

Also, through improvement of SDPF modeling accuracy, catalyst capacity may be decreased and manufacturing cost may be reduced.

For convenience in explanation and accurate definition in the appended claims, the terms “upper”, “lower”, “up”, “down”, “upwards”, “downwards”, “internal”, “outer”, “inside”, “outside”, “inwardly”, “outwardly”, “internal”, “external”, “front”, “rear”, “back”, “forwards”, and “backwards” are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described to explain certain principles of the invention and their practical application, to enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents. 

What is claimed is:
 1. Method of expecting N₂O generation according to oxidation of NH₃ in a selective catalytic reduction on diesel particulate filer (SDPF), comprising: measuring an initial NH₃ absorption amount in the SDPF; determining a first middle NH₃ absorption amount by subtracting an NH₃ slip amount in the SDPF from the initial NH₃ absorption amount in the SDPF; determining a second middle NH₃ absorption amount by subtracting an NH₃ amount oxidizing to NO_(x) and N₂ from the first middle NH₃ absorption amount; determining an N₂O generation amount in the SDPF; and determining a final NH₃ absorption amount in the SDPF by subtracting the N₂O generation amount from the second middle NH₃ absorption amount.
 2. The method of claim 1, wherein in determining the first middle NH₃ absorption amount, the NH₃ slip amount in the SDPF is a value determined by multiplying the initial NH₃ absorption amount and an NH₃ slip factor.
 3. The method of claim 1, wherein in determining the second middle NH₃ absorption amount, the NH₃ amount oxidizing to NO_(x) and N₂ is a value determined by multiplying the first middle NH₃ absorption amount and an oxidation factor oxidizing to NO_(x) and N₂.
 4. The method of claim 1, wherein in determining the N₂O generation amount in the SDPF, the N₂O generation amount is a value determined by multiplying the second middle NH₃ absorption amount and an N₂O generation factor.
 5. The method of claim 4, wherein the N₂O generation factor is determined by considering a selective catalyst reduction (SCR) catalyst temperature, an NH₃ absorption ratio in the SDPF, an exhaust gas flow amount, an NO density, and a degree of catalyst degradation.
 6. The method of claim 5, wherein the SCR catalyst temperature is determined by measuring a exhaust gas temperature.
 7. The method of claim 5, wherein an NO gas amount is determined by measuring an NO density.
 8. The method of claim 5, wherein the degree of catalyst degradation is determined by a catalyst degradation map applying a catalyst degradation factor.
 9. The method of claim 8, wherein the N₂O generation factor is determined by: determining a first value by applying the SCR catalyst temperature and the NH₃ absorption ratio in the SDPF to a first map; determining a second value by applying the exhaust gas flow amount and the NO density to a second map; determining a third value by applying the catalyst degradation factor to a third map; and multiplying the first value, the second value, and the third value together.
 10. The method of claim 1, further including: determining an N₂O slip amount by applying a transform constant using a map to the N₂O generation amount; and determining an NH₃ slip amount by subtracting the NO₂ generation amount from the initial NH₃ absorption amount in the SDPF. 